White House Director of Legislative Affairs Marc Short on Sunday said that he is “not aware” that President Donald Trump’s “ever” suggested that he would fire Robert Mueller, the special counsel overseeing the federal investigation into Russian interference in the 2016 election, though Trump reportedly tried to do so last year.

“I’m not aware of the President ever intimating that he wanted to fire Robert Mueller,” Short said on “Fox News Sunday.” “I’m not familiar in any conversation with the President ever intimating that he wanted to fire Robert Mueller.”

Short says that Trump has “been frustrated by this investigation.”

“He feels like there’s been millions of dollars in taxpayer dollars spent, and no evidence yet of collusion,” Short said. “The White House continues to cooperate in every manner providing any document that the special counsel has asked for.”

The New York Times on Thursday reported that Trump tried to fire Mueller last summer, but backed off when White House counsel Don McGahn said he would resign rather than fire the special counsel.